Hydrophilic interaction liquid chromatography (HILIC) has been developed as an chromatographic technique in separating highly polar compounds for the past few years [Alpert, A. J. J. Chromatogr. 1990, 499, 177-196; Strege, M. A. Anal. Chem. 1998, 70, 2439-2445; Strege, M. A. et al, Anal. Chem. 2000, 72, 4629-4633; Wang, X. D. et al, J. Chromatogr. A, 2005, 1083, 58-62]. The research of HILIC stationary phases is the basis for the development and application of HILIC. The conventional chromatographic stationary phases for normal phase liquid chromatography (NPLC), such as unmodified silica column, amino-based column, cyano-based column et al., can be directly used in HILIC [Guo, Y. et al, J. Chromatogr. A, 2005, 1074, 71-80; Garbis, S. D. et al, Anal. Chem. 2001, 73, 5358-5364]. However, the reproducibility is always poor and the service life of the columns is short. In recent years, novel polar stationary phases dedicated for HILIC such as amide-, hydroxyl- and zwitterionic functional group-modified stationary phase et al. have been successfully developed [Guo, Y. et al, J. Chromatogr. A, 2005, 1074, 71-80; Irgum, K. et al, J. Sep. Sci., 2006, 29, 1784-1821; Jandera, P., J. Sep. Sci., 2008, 31, 1421-1431]. The development of novel chromatographic stationary phases is of great significance for the research and application of HILIC.
The radical click reaction between thiol-ene and thiol-yne catalyzed by radical initiators has been widely used in the synthesis and modification of small molecules and polymers [Bowman, C. N. et al, Chem. Soc. Rev, 2010, 39, 1355-1387]. The click reaction possesses the characteristics of simplicity, high selectivity and high efficiency et al., thus it is very suitable for the preparation of chromatographic stationary phases.
Zwitterionic compounds which have high polarity and good hydrophilicity are well suited for hydrophilic interaction chromatographic stationary phase. The distribution of the oppositely charged groups on conventional zwitterionic HILIC stationary phases is perpendicular to the solid matrix and the surface charge of the stationary phase is difficult to adjust [W. Jiang et al, J. Chromatogr. A, 2006, 1127, 82-91]. The distribution of positive and negative charges is paralleled to the surface of the solid matrix on zwitterionic HILIC stationary phase prepared from compound with zwitterionic functional group at the end of it. And its surface charge can be adjusted and optimized by changing the pH values. However, no article involves such zwitterionic HILIC stationary phase has been reported and no product exists.